1. Field of the Invention
This invention relates to a semiconductor light emitting device used in indicators, message boards, or other visual display devices, which is improved in adherability of a resin encapsulating element and a resin stem, and also relates to a method for manufacturing same.
2. Description of the Prior Art
In conventional semiconductor light emitting devices, after a semiconductor light emitting element is mounted and bonded to a printed board with a printed wiring, a light-transmissive resin is injected into a cavity defined by a case mold capped onto the printed board to form an encapsulating element having a lens function.
These semiconductor light emitting devices are expensive, and the injected resin often leaks. Moreover, chips, unfilled portions or bubbles are liable to be made in the encapsulating element, resulting that the devices are not satisfactory in their appearances. Additionally, the use of an expensive printed board and a slow injection speed cause a high manufacturing cost.
On the other hand, a surface-packaged semiconductor light emitting device having no lens is as shown in FIG. 22. A resin stem 10 has formed a recess 7, and a semiconductor light emitting element 1 is put on the bottom of the recess 7. The sloped side walls 8 of the recess 7 functions as light reflective surfaces. Leads 21 and 22 are embedded in the resin stem 10. The leads 21, 22 are incorporated by molding a lead frame in form of a thin Fe- or Cu-based metal plate. The resin stem 10 is made by injection-molding a thermoplastic resin such as polycarbonate (PC) containing a filler agent such as silica (SiO.sub.2) together with the lead frame. End portions of the leads 21, 22 for contact with the semiconductor light emitting element lie on the bottom surface of the recess 7 of the resin stem 10. The semiconductor light element 1 is mounted on the lead 21 by conductive paste 3, or the like, containing silver (Ag), for example. A first electrode of the semiconductor light emitting element 1 is connected to the lead 21, and a second electrode is electrically connected to the lead 22. The second electrode and the lead 22 are connected by a bonding wire 4 of gold (Au), for example. A light-transmissive resin encapsulating element 5 of a thermosetting resin is applied onto the resin stem 10 so as to cover these end portions of the leads 21, 22, semiconductor light emitting element 1 and bonding wire 4.
However, the surface-packaged semiconductor light emitting device shown in FIG. 22 has no lens, and is unreliable in adherability between the resin encapsulating element of a thermosetting resin and a resin stem of a thermoplastic resin.